1. Field of the Invention
The invention generally relates to a brake control apparatus and method for controlling the brakes of a vehicle, and more particularly, to a brake control apparatus, and method for controlling the brakes of a vehicle, in which an actuator changes a wheel cylinder pressure.
2. Description of the Related Art
Generally, many vehicles have electronically controlled braking systems as disclosed in JP-A-2001-163198. In such electronically controlled braking systems, the wheel cylinder pressure of each wheel is controlled so that an appropriate braking force is applied to each wheel when the vehicle operator operates a brake pedal. Such electronically controlled braking systems generally have an actuator, such as a linear solenoid valve, that increases or decreases the wheel cylinder pressure. Such an actuator may produce self-excited vibrations caused by, for example, the flow of hydraulic fluid therein. The self-excited vibrations of the actuator may be transmitted to the body of the vehicle through an oil pressure supply/discharge pipe via the hydraulic fluid and make abnormal noise. JP-A-11-240430 discloses, for example, an automatic braking apparatus that includes a pressure-reducing valve controller, which opens a pressure-reducing valve for a predetermined period that covers the time before and after the opening or closing of a pressure-increasing valve when increase of the wheel cylinder pressure begins or end.
Such an actuator may produce self-excited vibrations when the pressure change rate for changing the wheel cylinder pressure, the amount of change in pressure, or the volume of fluid flowing through the linear solenoid valve is large. The references discussed above do not describe how to reduce such self-excited vibrations.